I tell students, you speak like someone from Pergamos, I like Alexandrians. We talk differently, what matters is that we understand each other. When you read a text, you 'hear' sounds (in your mind) whether you speak them or not. What is important is 2 things: (1) Be consistent in how you pronounce syllables (vowels, diphthongs, consonants, and consonant clusters), and (2) Use stress accent on the correct syllable (or if your language or language accent scheme is tonal, develop a pronunciation scheme that consistently pronounces accents on the syllables the accent occurs.

Having a standard to start with is important. Restored pronunciation is fine, it has good historical linguistic backing, and is a nice place to start. Of course, everyone is going to sound a little bit different with it, just like learning any second language as an adult. A good solid Brit (as opposed to a bad, frail Brit? Sorry... ) is going to sound different speaking ancient Greek than someone from the American Heartland, even if they both strive diligently to use their restored pronunication. But they will be be able to understand each other, and, after a bit of practice and listening, also understand Erasmean or restored Attic and the like.

The terminology is confused. Some people use Restored as a product name and promote it (bad!). Others seem to imply that Erasmean is :or: is not equal to Restored. People preoccupied with pronunciation are wasting energy that could be spent more profitably on learning syntax. Heard some guys in Europe who were chatting together rapidly in Ancient Greek and were using sentence structure that sounded like Dick and Jane from the 1950s. See Spot run.

Now, for some reason I'm quite flexible with pronunciation schemes for Ancient Greek, but the only valid pronunciation system for Latin is the Classical. Away with the Ecclesiastical. If it was good enough for Caesar, it's good enough for me!

Nonsense. If it was good enough for Augustine, it's good enough for me!

I think that there are different things in mind when talking of being useful here.

I find Buth's pronunciation scheme to be useful when thinking about textual variants. I also find it useful when discussing the text with a Greek colleague; she can understand me a lot more easily now that I am using this pronunciation - with Erasmian she looked at me like an alien

I am guessing that reading non-biblical texts and seeing spelling variants will be a lot easier when keeping in mind the phonology in line with what they would have heard themselves

Is it useful for reading the biblical text itself, not really. That doesn't however mean that it is not useful

Further, if we can reconstruct what it sounded like originally, why wouldn't we consider that as a worthwhile thing rather than starting with a pronunciation that we know is wrong?

I guess I am just saying that dismissing it as pointless misses some of its benefits. That said - being preoccupied with it to the detriment of learning the syntax and the discourse analysis is bad as Stirling says

I am guessing that reading non-biblical texts and seeing spelling variants will be a lot easier when keeping in mind the phonology in line with what they would have heard themselves.

We don't know what they would have heard themselves. I suspect that first century Greek spoken in Jerusalem was like English in Seattle. When a large percentage of the speakers are using it as a second language standards of pronunciation become very broad and you forced to adapt to wildly diverse and irregular sounds. Living in a port city where native speakers of English are a minority in many neighborhoods and you have over a hundred language groups within a ten mile radius, you encounter this in your face every day. The whole idea of recovering the sound is questionable.

develop a pronunciation scheme that consistently pronounces accents on the syllables the accent occurs.

Correct accent is more important than people realize, I think. To illustrate it, take an English word and mispronounce the accent. Take the same word and mispronounce a couple letters, but keep the right accent.